Attention is directed to an article by three of the inventors herein entitled "Spatially delineated growth of metal films via photochemical prenucleation" in Vol. 38, No. 11 of Applied Physics Letters (June 1981), incorporated herein by reference. Attention is also directed to U.S. patent application Ser. No. 150,816 by Deutsch et al. entitled "Method and Apparatus for Depositing a Material on a Surface" filed May 19, 1980, disclosing a technique for depositing materials by laserinduced photo-disassociation of a fluid medium, also incorporated herein by reference.
Conventionally, the growth of patterned thin metallic films is accomplished by the use of photolithographic masks. For example, an etch-resistant coating ("a resist") is laid down upon a semiconductor wafer. A pattern is created by further coating portions of the resist with an opaque material and then irradiating the material to break down the exposed resist. The exposed resist is then removed by developing and the wafer may then be etched and metallized to produce a patterned film. The above example illustrates positive resists, wherein the pattern which remains after development corresponds to the opaque regions. Negative resists are also known in the art.
Maskless growth of two dimensionally patterned thin films would be an important processing capability for both the microelectronics and photovoltaics industry. Elimination of the necessity of masking during thin-film growth would reduce the complexity and number of steps in, say, the metallization step in IC-chip formation or, even more important, in the metallization of contacts for photovoltaic solar cells Further, it would make it economical to produce custom or one-of-a-kind designs--since the expensive mask production step is eliminated. Thus, there exists a need for methods and apparatus for growing patterned films without masks.